JPH0931402A - Production of carbon-based conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a carbon-based conductive paste capable of forming carbon coating good in conductivity and adhesiveness. SOLUTION: This production of a carbon-based conductive paste is to mix, knead and disperse carbon black acarboneous powder comprising natural flaky graphite having 10-20μm average particle size together with polyvinyl butyral and a titanate-based coupling agent with a resol type phenolic resin dissolved in an organic solvent. The carbon black having 115-170cc absorption amount of dibutyl phthalate per 100g of catrbon black can be preferably used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermosetting carbon-based conductive paste for forming a conductive circuit composed of a carbon coating on a printed circuit board.

[0002]

2. Description of the Related Art A conductive paste is applied to the inner surface of a case forming member of a printed wiring board or an electronic device and cured by heat or an electron beam to form a film, which has a function of a conductive circuit, an electromagnetic wave shield, an electrostatic shield, etc. Techniques for forming a conductive coating are known. Such conductive paste includes
There are those that use metallic powder such as silver and copper as conductive particles and those that use carbonaceous powder such as graphite and carbon black.A conductive coating made of conductive paste using metallic powder is generally an electrically conductive material. The sheet resistance is about 0.1 to 1 Ω / □, but in the case of silver powder, migration may occur depending on the use environment,
In the case of copper powder, there is concern that the resistance value may change due to oxidation.

On the other hand, the carbon-based conductive paste using carbonaceous powder as conductive particles uses phenolic resin, epoxy resin, alkyd resin by using carbonaceous powder such as graphite and carbon black alone or in combination. Kneading in a cellosolve or carbitol-based organic solvent together with a binder and a dispersant consisting of a curable resin such as
It is dispersed. As the dispersant, thermoplastic natural or synthetic polymer materials such as ethyl cellulose, nitrocellulose, hydroxycellulose, polyvinyl butyral, and polyvinyl acetate are used, as well as silane-based, titanate-based, and aluminum-based coupling agents, and nonionic A method of adding a surfactant to improve dispersibility is known. This carbon-based conductive paste,
A carbon film printed on a printed wiring board such as paper phenol or glass epoxy by a screen printing method and subjected to a curing treatment is used for a key contact or a slide switch of a printed circuit board. These applications utilize the sliding characteristics of the contained graphite.

The carbon coating formed on the printed wiring board by screen printing has an average thickness (film thickness) of about 2
0 μm, the sheet resistance representing the electric conductivity of the film is 20 to 50 Ω / □, that is, the specific resistance is 0.04 to 0.1.
Ω · cm, which is inferior in electric conductivity to the above-mentioned coating made of metal-based powder, but due to the characteristics of carbon-based conductive particles, migration that occurs when the conductive particles are silver, or when copper is used. Stable conductivity characteristics are shown without concern about increase in resistance due to oxidation. For this reason, methods for lowering the resistance value of the conductive coating made of a carbon-based conductive paste have been studied for some time. For example, JP-A-60-30102 discloses a method of using expanded graphite as conductive particles. . In addition, JP-A-54-
Japanese Patent No. 36343 discloses a method of using highly conductive carbon black.

[0005]

However, expanded graphite has a very low bulk density of 0.03 to 0.2 g / cm ^3, and it is difficult to handle the powder such as material blending and transportation. In addition, an extremely large amount of solvent is required in order to form a paint (paste) and obtain a paste viscosity suitable for screen printing. Here, as the solvent, a cellosolve- or carbitol-based organic solvent is mainly used. When screen printing is performed on a printed wiring board with a paste containing a large amount of a solvent as described above, the coating film has a rough surface, and the thermally cured carbon coating film falls off. The powder falling means that a part of the particles peels off from the surface of the coating film, which may cause unnecessary conduction between the insulating parts. Furthermore, in the printed pattern after screen printing, bleeding occurs at the end of the desired pattern, making it difficult to form a practical carbon coating for circuit formation. In addition, since a strong acid is used in the process of manufacturing expanded graphite, residual acid may attack the copper foil on the printed wiring board. It is necessary to apply heat treatment.

On the other hand, although carbon black having a large specific surface area is known to exhibit high conductivity, such carbon black generally has a low binding force with a curable resin which is a binder and is hardened. If this is done, cracks will occur in the coating. As a result, the electric resistance value of the conductive coating increases.
Furthermore, since an excessive amount of solvent is required to adjust the paste viscosity suitable for screen printing, the actual effective solid content in the paste is low, and the film thickness of the resulting coating is small, which reduces the electrical conductivity of the wiring part. The resistance value becomes high. As a countermeasure against this, it is possible to increase the ratio of the conductive particles to the thermosetting resin as the binder. As a result, a slight decrease in the resistance value is recognized, but the binder amount is relatively insufficient. There are problems such as a decrease in the adhesion of the coating film to the printed wiring board and the occurrence of cracks in the coating film due to changes in thermal expansion during soldering considering the mounting process.

An object of the present invention is to provide a method for producing a carbon-based conductive paste, which makes it possible to obtain a carbon coating film having improved electric conductivity by utilizing the stability of carbonaceous powder as described above. .

[0008]

In view of the above problems, the present inventors have completed this invention as a result of intensive research. That is, the present invention relates to a polyvinyl butyral and a titanate coupling agent in which a carbonaceous powder composed of carbon black and natural scaly graphite having an average particle size of 10 to 20 μm is added to a resol type phenol resin dissolved in an organic solvent. In the method for producing a carbon-based conductive paste, which is kneaded and dispersed together, a dibutyl phthalate (hereinafter referred to as “DBP”) oil absorption is 100 g.
The purpose of the present invention is to provide a method for producing a carbon-based conductive paste, which is characterized by using 115 to 170 cc of carbon black. Further, in the above-mentioned production method, (a) the weight average molecular weight of the resol-type phenol resin is 1100 to 1530, and (b) the blending amount of the natural scaly graphite and carbon black of the carbonaceous powder is 50 by weight. : 50 to 70:30, and (c) the blending amount of the effective solid content of the carbonaceous powder and the resol-type phenol resin is 50:50 to 60:40 by weight.
(D) The polyvinyl butyral is used as the carbonaceous powder 10
2 to 6 parts by weight with respect to 0 parts by weight, and (e) 8 to 12 parts by weight of the titanate coupling agent is added to 100 parts by weight of the carbon black. The present invention provides a method for manufacturing the same.

In the present invention, the DBP oil absorption, which is a physical property suggesting the specific surface area and the structural state of carbon black, is 115 to 170 cc per 100 g.
Carbon black and natural flake graphite having good electric conductivity, in a predetermined mixing ratio, in a specific molecular weight resol type phenol resin, together with polyvinyl butyral as a dispersant, a titanate coupling agent and an organic solvent. This is a method for producing a carbon-based conductive paste that is made into a paste by kneading and dispersing. The electrical conductivity of the carbon coating formed by the paste prepared by the manufacturing method of the present invention is good, and when expressed in terms of sheet resistance value, it is 1 / 100th that of the coating obtained from the conventional carbon-based conductive paste.
It is about 4 to 1/3 and shows a value of 10Ω / □ or less.

DB of carbon black used in the present invention
The P oil absorption is 115 to 170 cc per 100 g,
It is preferably 129 to 155 cc. When carbon black having a DBP oil absorption of more than 170 cc per 100 g is used, 50% by weight or more of an organic solvent is required in the paste as described above. The coating film formed by such a paste does not undergo sufficient evaporation with the thermosetting binder because the organic solvent rapidly evaporates in the thermosetting process after printing and the specific surface area of carbon black is extremely large. As a result, the binding force is reduced and the coating film is cracked. As a result, the electric resistance value of the film increases, and the adhesion between the film and the printed wiring board decreases. On the other hand, in the case of carbon black having a DBP oil absorption of less than 115 cc per 100 g, the number of contact points for electrical conduction in the coating is insufficient due to insufficient structure development, resulting in high contact resistance and electrical conductivity. Can't get a good one.

Further, from the viewpoint of preventing clogging of the screen mask, it is general that the maximum particle size of graphite, which is the other conductive particle, is 100 μm or less. The average particle size of graphite used in the present invention is 10 to 20 μm.
m, preferably 12 to 18 μm, particularly preferably 14 to
16 μm. If the particle size is less than 10 μm, the particles are too fine and the contact resistance increases, and the electric resistance value increases. On the contrary, when the particle size is larger than 20 μm, the particles are too coarse,
The surface of the formed film becomes rough. A coating having a large surface roughness is likely to cause powder drop, which may cause unnecessary conduction between insulating portions, which is a problem.

The weight average molecular weight of the resol type phenolic resin is also a factor that affects the electric conductivity of the obtained coating film. The weight average molecular weight of the resol-type phenol resin used in the method of the present invention is 1100 to 1530, and the larger the molecular weight, the more preferable. When the weight average molecular weight is less than 1100, the phenol resin and the conductive particles have high wettability, so that the resin coats the conductive particles, and when the resin is formed into a film, the insulating resin intervenes between the conductive particles. The electric resistance value becomes high. Furthermore, since the shrinkage stress during heat curing of the coating film is large, the adhesion of the formed coating film to the substrate is reduced, and when exposed to a high temperature atmosphere such as soldering considering the mounting process on the printed circuit board, The change in resistance of the coating becomes large. Resins having a weight average molecular weight of more than 1530 are generally not available at present,
This was the upper limit.

The carbonaceous powder contains natural scaly graphite and carbon black having a specific DBP oil absorption in an amount of 50:50 to 70:30, preferably 55:45.
65:35, particularly preferably 58:42 to 62:38. The particle size of carbon black is about 1/1000 to 1/100 of that of natural scaly graphite, and carbon black is filled in the carbon coating so as to fill the gaps of natural scaly graphite to improve electrical conductivity. To work.
Here, if the ratio of carbon black in the carbonaceous powder exceeds 50% by weight, the amount of fine conductive particles becomes large, the contact resistance increases, and the electric conductivity of the formed coating film decreases. Also, if it is less than 30% by weight, the gap between the graphite particles cannot be sufficiently filled with carbon black, so that the contact state between the conductive particles becomes insufficient and the electric conductivity is lowered.

The resole-type phenol resin is handled in a liquid form in which the above-mentioned resole-type phenol resin having a specific weight average molecular weight is dissolved in a cellosolve or carbitol-type organic solvent of the same type as the pasting organic solvent. Therefore, in order to mix an accurate amount of the phenol resin, it is necessary to express the solid content of the actual phenol resin in the liquid, that is, the “effective solid content”. In the present invention, the blending amount of the carbonaceous powder and the effective solid content of the resol type phenol resin is 50:50 to 60:40, preferably 55: 4 by weight ratio.
5 to 60:40, particularly preferably 57:43 to 60: 4
Set to 0. When the blending amount of the effective solid content of the phenol resin exceeds 50% by weight with respect to the carbonaceous powder, the amount of resin coating the carbonaceous powder of the conductive particles increases. Since the phenol resin is an insulator, the electric conductivity between the conductive particles is lowered and the electric resistance value is increased when it is formed into a film. On the other hand, when the blending amount of the phenol resin is less than 40% by weight, the binding force between the conductive particles is reduced, the contact state of the conductive particles becomes insufficient, and good electrical conductivity cannot be obtained. Furthermore, the adhesion of the carbon coating to the printed wiring board deteriorates.

Even if the specifications of the above-mentioned conductive particles, phenol resin, etc. and the mixing amounts thereof are the same, the electric conductivity of the coating film changes depending on the dispersed state of the conductive particles in the paste. That is, when comparing the paste in the state in which the conductive particles are agglomerated and the paste in the dispersed state, respectively, the coating film made of the paste in which the conductive particles are agglomerated has a higher resistance value, and the mounting process is also taken into consideration. The change in resistance value due to the heat history is large. Therefore, the better the dispersed state of the conductive particles in the coating material (paste), the lower the resistance value of the coating film, which is preferable.

The present invention is characterized in that the amount of polyvinyl butyral, which is a dispersant for the carbon-based conductive paste, is 2 to 6 parts by weight with respect to 100 parts by weight of the carbonaceous powder. If the amount of the dispersant is less than 2 parts by weight, a good dispersed state cannot be obtained. On the other hand, if the amount of the dispersant exceeds 6 parts by weight, the dispersed state does not improve further, and the insulating component increases. Therefore, the object of the present invention cannot be achieved because the resistance value is increased.

Further, the titanate coupling agent in the present invention is characterized by being added in an amount of 8 to 12 parts by weight with respect to 100 parts by weight of carbon black having the specific DBP oil absorption. When it is less than 8 parts by weight, good dispersibility cannot be achieved, and when it exceeds 12 parts by weight, no change in dispersibility is observed and the adhesion of the coating film to the substrate is extremely lowered. The titanate coupling agent forms a compound of titanium and carbon by heat denaturation and solidifies, but the boiling point of each coupling agent exceeds 200 ° C, and the temperature is limited to about 150 ° C for carbon coating. Only the amount given is heat denatured. Therefore, when the amount of the coupling agent added is increased, the coupling agent remains in a liquid state in the coating film, and the adhesion of the carbon coating film to the printed wiring board decreases.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In a resole-type phenol resin dissolved in an organic solvent, dibutyl phthalate oil absorption is 115
~ 170 cc of carbon black and average particle size of 10
Carbonaceous powder consisting of 20 μm of natural flake graphite
By kneading and dispersing with a polyvinyl butyral dispersant and a titanate coupling agent,
A carbon-based conductive paste capable of forming a carbon coating having excellent stability and electric conductivity is manufactured.

[0019]

EXAMPLES The present invention will be described in more detail with reference to the following examples. <Example 1> (Examples 1 to 4 and Comparative samples 1 to 3) Dependence of carbon black on DBP oil absorption (Adjustment of paste) Natural flaky shape having an average particle size of 16 μm (particle size range of 2 to 85 μm) Graphite (Brand name: BF-1
6A, manufactured by Chuetsu Graphite Co., Ltd., carbon black and resol type phenol resin, polyvinyl butyral as a dispersant (trade name: S-REC BH-S, Sekisui Chemical Co., Ltd.)
And titanate coupling agent (trade name: Plenact KR9SA, manufactured by Ajinomoto Co., Inc.) were weighed in the following proportions, butyl cellosolve as an organic solvent was appropriately added, and the mixture was mixed with a likai machine, followed by kneading with a three-roll mill. did. Finally, butyl cellosolve was added to adjust the viscosity of the paste to prepare a carbon-based conductive paste. The weight average molecular weight of the above-mentioned resol type phenol resin is 1460. Component Weight part Black lead 60 Carbon black 40 Resol type phenolic resin (as solid content) 67 Polyvinyl butyral resin 4 Titanate coupling agent 4 Butyl cellosolve Suitable (Preparation of carbon coating) Made of steel wire, emulsion thickness is 20μm
1mm wide and 10mm long on a printed wiring board made of paper phenol using a 200 mesh screen mask
The wiring pattern of No. 1 was screen-printed and subjected to thermosetting treatment at 150 ° C. for 15 minutes to form a carbon film. (Evaluation of Sample) The electric resistance value of the coating film obtained as described above was measured with a digital multimeter, the film thickness was measured with a surface roughness meter, and the film thickness of 20 μm was measured using the following formula [I]. The sheet resistance value (Ω / □) at that time was determined.

[Equation 1] Here, R is the resistance value (Ω) of the wiring portion, w is the coating film width (m
m) and t are coating film thickness (μm), and 1 is coating film length (mm). Further, the adhesion of the coating film to the substrate was evaluated by forming a carbon coating film on a copper foil, immersing the substrate in a solder (composition Sn-40Pb) bath at 260 ° C. for 10 seconds, allowing to cool, and then using a cellophane tape. It was adhered and the presence or absence of peeling of the carbon coating was confirmed. Table 1 shows the specifications of 7 carbon blacks used in the test and the characteristics of the carbon coatings obtained from various pastes. The example has 4 points, and the comparative example has 3 points.

[0020]

[Table 1]

Samples 1 to 4 having a DBP oil absorption within the range of the present invention have good electrical conductivity with a sheet resistance value of 10 Ω / □ or less and good adhesion to the substrate. Above all, DBP oil absorption is 129-155cc / 100g
(Samples 2 and 3) are particularly excellent in electrical conductivity. On the other hand, the comparative sample 1 having a low DBP oil absorption has a sheet resistance value of 30 Ω / □ and is as electrically conductive as a carbon film formed by a conventional carbon-based conductive paste. It is considered that this is because the contact between the conductive particles is not sufficient due to the immature structure development. On the other hand, among the comparative samples 2 and 3 having a DBP oil absorption exceeding the range of the present invention, the comparative sample 2 having a DBP oil absorption of 210 cc / 100 g has good adhesion, but has a decrease in binding force due to the binder and The contact resistance becomes high, and good electrical conductivity cannot be obtained. Further, the comparative sample 3 having a high DBP oil absorption amount of 360 cc / 100 g was also defective because the adhesion was lowered. In addition, the amount of butyl cellosolve as a solvent used in forming a paste is 50 to 60% by weight of the paste.
After printing, bleeding was seen at the edge of the wiring pattern.

<Example 2> (Working Samples 5 to 7, Comparative Samples 4 and 5) The dependence of the weight average molecular weight of the resole type phenolic resin will be examined. The carbon black used had a DBP oil absorption of 129 cc / 100 g. Further, the compounding amount of each material for forming a paste was in accordance with Example 1. Table 2 shows the specifications of 5 points of resol type phenol resin used in the test and the characteristics of the carbon coatings obtained from various pastes. In addition, here, there are 3 points for the execution sample and 2 points for the comparison sample.
It is a point.

[0023]

[Table 2]

The sample Nos. 5 to 7 in which the weight average molecular weight of the resol-type phenol resin is within the range of the present invention have good electrical conductivity with a sheet resistance value of 10 Ω / □ or less and good adhesion to the substrate. Is. Among them, the one having the highest weight average molecular weight of 1460 (Sample 7) is particularly excellent in electrical conductivity. On the other hand, in Comparative Samples 4 and 5 in which the weight average molecular weight of the resol type phenolic resin is low, the wettability of the resin with respect to the carbonaceous powder as the conductive particles is high and the surface of the carbonaceous powder is covered with the resin. Good electrical conductivity cannot be obtained. Further, since the shrinkage stress during heat curing is large, the adhesion of the coating film to the printed wiring board is poor.

<Example 3> (Examples 8 to 10 and comparative samples 6 and 7) The dependence of the carbonaceous powder on the blending ratio by weight of graphite and carbon black will be examined. As the graphite, a natural flake graphite having an average particle size of 16 μm (particle size range of 2 to 85 μm) (trade name: BF-16A, manufactured by Chuetsu Graphite Co., Ltd.) is used, and as the carbon black, DBP oil absorption is 129 cc / 100.
The total amount of carbonaceous powder was 100 parts by weight, and the other materials were mixed in the same manner as in Example 1. The type of carbon powder used in the test was 5 points, of which 3 points were the actual samples and 2 points were the comparative samples. These characteristics are shown in Table 3.

[0026]

[Table 3]

Samples 8 to 10 in which the weight ratio of graphite and carbon black in the carbonaceous powder is within the scope of the present invention.
Has good electrical conductivity with a sheet resistance value of 10Ω / □ or less, and has good adhesion to a printed wiring board. Above all, the weight mixing ratio of graphite and carbon black is 6
The sample of 0:40 (Sample 9) is particularly excellent in electrical conductivity. On the other hand, the electrical conductivity of the coating of Comparative Sample 6 in which the amount of carbon black contained in the carbonaceous powder is large is low. On the contrary, the comparative sample 7 in which the amount of graphite in the carbonaceous powder is large also has low electric conductivity.

<Example 4> (Examples 11 to 13 and comparative samples 8 and 9) The dependence of the weight ratio of the effective solid content of the resol type phenolic resin to the carbonaceous powder (graphite and carbon black) will be examined. In addition, as the graphite, natural flake graphite having an average particle diameter of 16 μm (particle diameter range of 2 to 85 μm) (trade name: BF-16A, manufactured by Chuetsu Graphite Co., Ltd.) is used, and as the carbon black, a DBP oil absorption amount is used. Is 129cc
/ 100 g was used, and as the resol-type phenol resin, one having a weight average molecular weight of 1460 was used. The total amount of the carbonaceous powder was 100 parts by weight, the compounding amount of the phenol resin was changed, and the compounding of the other materials was the same as in Example 1. The type of formulation used in the test was 5 points, the execution sample was 3 points, and the comparative sample was 2 points.
Their characteristics are shown in Table 4.

[0029]

[Table 4]

The sheet resistance values of the practical samples 11 to 13 in which the weight ratio of the effective solid content of the resol type phenolic resin to the carbonaceous powder is within the range of the present invention are 10 Ω / □.
It has the following good electrical conductivity and good adhesion to the substrate. Among them, the one having a weight compounding ratio of the phenol resin to the carbonaceous powder of 60:40 (Sample 13) is particularly excellent in electric conductivity. On the other hand, Comparative Sample 8 in which the amount of the phenolic resin is larger than that of the carbonaceous powder has good adhesion, but the amount of the carbonaceous powder as the conductive material is small and the sheet resistance value is high. On the other hand, in Comparative Sample 9, the sheet resistance value is not so high, but the adhesion is not good.

<Example 5> (Examples 14 to 16 and comparative samples 10 and 11) The dependence of the addition amount of polyvinyl butyral on the carbonaceous powder (graphite and carbon black) will be examined. Note that graphite has an average particle size of 16 μm (particle size range of 2 to 85).
(μm) natural scaly graphite (trade name: BF-16A, manufactured by Chuetsu Graphite Co., Ltd.), and carbon black having a DBP oil absorption of 129 cc / 100 g was used. 60 / both
The resol type phenolic resin has a weight average molecular weight of 1460, the total amount of carbonaceous powder is 100 parts by weight, and the addition amount of polyvinyl butyral is changed. The composition was the same as in Example 1. The type of formulation used in the test was 5 points, the execution sample was 3 points and the comparative sample was 2 points. Their characteristics are shown in Table 5.

[0032]

[Table 5]

Practical samples 14 to 16 in which the amount of polyvinyl butyral added to the carbonaceous powder was within the range of the present invention.
Has good electrical conductivity with a sheet resistance value of 10 Ω / □ or less, and also has good adhesion of the coating film to the printed wiring board. Among them, the sample (Sample 15) in which the amount of polyvinyl butyral added was 4 parts by weight is particularly excellent in electrical conductivity. On the other hand, in the comparative sample 10 containing no polyvinyl butyral, the conductive carbonaceous powder, in particular, the natural scaly graphite is not sufficiently dispersed, and a good electrical conductivity cannot be obtained. On the other hand, in Comparative sample 11, the sheet resistance value was further increased because the amount of polyvinyl butyral added was too large.

<Example 6> (Examples 17 to 19, Comparative Samples 12 and 13) Of carbonaceous powders, the dependence of the addition amount of the titanate coupling agent on carbon black will be examined.
Note that graphite has an average particle size of 16 μm (particle size range of 2 to 85).
(μm) natural scaly graphite (trade name: BF-16A, manufactured by Chuetsu Graphite Co., Ltd.), and carbon black having a DBP oil absorption of 129 cc / 100 g was used. 60 / both
40 parts by weight, and the resol type phenol resin has a weight average molecular weight of 1460, the total amount of carbonaceous powder is 100 parts by weight, and the addition amount of the coupling agent is changed, The composition was the same as in Example 1. The type of formulation used in the test is 5 points, of which 3 points are the practical samples and 2 points are the comparative samples. Their characteristics are shown in Table 6.

[0035]

[Table 6]

Practical samples 17 to 19 in which the addition amount of the titanate coupling agent to the carbon black was within the range of the present invention had a good sheet conductivity of 10 Ω / □ or less, and had good electrical conductivity. Adhesion is also good. On the other hand, the comparative sample 12 containing a small amount of the coupling agent had an insufficient dispersed state of carbon black among the carbonaceous powders, so that the coating was not dense and good electrical conductivity was obtained. Absent. On the other hand, in Comparative Sample 13 in which the amount of the coupling agent added was large, the coupling agent remained in the film, and the electrical conductivity was also poor, and the value was 150
The coupling agent remains liquid in the coating even after the thermosetting treatment at ℃, so that the adhesion of the coating to the substrate is lowered and the coating is peeled off.

[0037]

The structure of the carbon-based conductive paste according to the manufacturing method of the present invention is as described above, but the carbon coating formed by this paste has a sheet resistance higher than that of the coating formed by the conventional carbon-based conductive paste. The value is 1
It is as low as about / 4 to 1/3 and exhibits high electrical conductivity. Carbon-based conductive coatings are not as good in electrical conductivity as conductive coatings made of metallic powders, but there are no problems such as migration in silver powders or oxidation in copper powders. Makes it possible to replace the coating made of metal powder with a carbon coating, and a new application of the carbon-based conductive paste can be expected.

Claims (2)

[Claims] 1. A carbon black and an average particle diameter of 10 to 20 in a resol type phenol resin dissolved in an organic solvent.
In the method for producing a carbon-based conductive paste, which comprises kneading and dispersing a carbonaceous powder composed of natural scaly graphite having a diameter of μm together with polyvinyl butyral and a titanate-based coupling agent, the carbon black is dibutyl phthalate (DBP) oil absorption amount. Is 115 to 100g
A method for producing a carbon-based conductive paste, which comprises using 170 cc of carbon black. 2. The weight average molecular weight of (a) the resol type phenolic resin is 1100 to 1530, and (b) the blending amount of the natural scaly graphite and carbon black of the carbonaceous powder is 50:50 by weight. ~ 70: 30,
(C) The blending amount of the effective solid content of the carbonaceous powder and the resol-type phenol resin is 50:50 to 60: 4 in weight ratio.
0, (d) 2 to 6 parts by weight of the polyvinyl butyral is added to 100 parts by weight of the carbonaceous powder,
(E) The method for producing a carbon-based conductive paste according to claim 1, wherein 8 to 12 parts by weight of the titanate-based coupling agent is added to 100 parts by weight of the carbon black.